Micro ch 22

• Diphtherioids
• Staphylococci
• Fungi

*has lots of chicken wire

Has Capsule - inhibits phagocytosis

Clumping factor - attaches bacterium to fibrin, fibrinogen, & plastic devices

Coagulase- May slow progress of leukocytes into infected area by producing clots in surrounding capillaries

Enterotoxins: Superantigens cause food poisoning inf ingested, cause toxic shock if systemic

Exfoliatin: Separates layers of epidermis, causing scalded skin syndrome

Fibronectin-binding protein: Attaches bacterium to acellular tissue substances, endothelium, epithelium, clots, indwelling plastic devices

Hyaluronidase: Breaks down hyaluronic acid component of tissue, thereby allowing infection to spread

Leukocidin: kills neutrophils or causes them to release their enzymes

Lipase: breaks down fats by hydrolyzing bond btwn glycerol and fatty acids

Proteases: degrade collagen and other tissue proteins

Protein A: Binds to Fc portion of antibody, thereby interfering with opsonization

Toxic shock syndrome toxin: causes rash, diarrhea, and shock

-toxin: makes holes in host cell membranes

• Acne
• Hair follicle infections
• Staph. Scalded skin syndrome
• Impetigo
• Rocky mtn spotted fever
• Lyme disease

"Sorry, I Hate Acne Too!"

Typically caused by Propionibacterium acne

inflammation of one or more hair follicles, causing small red bumps, or pimples

• Boil
• If infection from folliculitis extends from follicle to adjacent tissues & causes localized redness, swelling, severe tenderness and pain
• Pus may drain from boil along with plug of inflammatory cells and dead tissue

• A worsened furuncle (boil)
• large area of redness, swelling, and pain with several sites of draining pus
• usually develop in areas of the body where skin is thick, such as back of neck
• Fever is often present

• *Staphylococcal scalded skin syndrome
• S/S: sensitive red rash with sandpaper texture, malaise, irritable, fever, large blisters, peeling of skin

Cause: Strains of Staphylococcus aureus that produce exfoliatin toxin

• Exfoliatin is produced by organisms at an infection site, usually of skin, and carried by bloodstream to the epidermis where it causes a split in cellular layer
• Loss of body fluid and secondary infections contribute to mortality

Epidemiology: Person to person transmission; seen mainly in infants, but can occur at any age

• Tx: with penicillinase-resistant penicillins
• Removal of dead tissue
• Isolate pt to prevent 2nd infection and to limit spread of diease

most common type of pyoderma (a skin infection characterized by pus production) 

S/S: Blisters that break, releasing plasma and pus; formation of golden-colored crusts; lymph node enlargement

Cause: Can be caused by BOTH STREPTOCOCCUS PYOGENES AND STAPHYLOCOCCUS AUREUS

Organisms entering skin through minor breaks; certain strains that cause impetigo can also cause glomerulonephritis

Epi: Spread by direct contact with carriers or pts with impetigo, insects, and fomites

• Tx: oral penicillin if cause is known to be S.pyogenes; otherwise, an anti-staphylococcal antibiotic orally or topically
• Cleanliness; care of skin injuries

Strep pyogenes: chains of gram-pos cocci

Staph Aureus: clusters of gram-pos cocci

Strep Pyogenes: Beta-hemolytic; Cat+, Coagulase -; Obligate fermenter

Staph Aureus: Golden, hemolytic colonies, Cat +, Coagulase +, facultative anaerobe

S/S: HA, pains in muscles & joints, fever, followed by hemorrhagic rash that begins on extremities

Cause: Rickettsia rickettsii, an obligate intracellular bacterium

• Organisms multiply at site of tick bite
• Invade bloodstread and infect endothelial cells
• Vascular lesions and immune response to endotoxin account for pathologic changes

Epi: Zoonosis transmitted by bite of infected tick, Usually Dermacentor sp.

• Tx: Doxycycline or chloramphenicol
• Prevented by avoiding tick-infested areas, using tick repellent, removal of ticks within 4 hours

• S/S:
• Early localized infection: Enlarging rash at site of bite. Lymph node enlargement near bite, flu like sx.
• Early disseminated infection: Heart and nervous system involvement
• late persistent infection: Chronic arthritis and nervous system impairment

Cause: Borrelia burgdorferi, a spirochete

Dr. Willy Burgdorfer, at Rocky Mt Labs in Montana

• Spirochetes injected into skin by infected tick multiply and spread radially (rash makes bulls eye)
• Spirochetes enter bloodstream and are carried throughout body
• Immune reaction to bacterial antigen causes issue damage

Spread by bit of ticks, usually found in association with animals such as white-footed mice and white-tailed deer living in wooded areas

• Early tx with doxycycline and others
• Prolonged antibiotic therapy in chronic cases
• Protective clothing & tick repellents

• Varicella
• Rubeola (measles)
• Rubella (German measles)
• Warts (dermal warts)

• 1. inhaled & infects nose and throat
• 2. Infects nearby lymph nodes, reproduces and enters bloodstream
• 3. infection of other body cells occurs, resulting in showers of virions into bloodstream
• 4. Immune system eliminates infection except for some virions inside nerve cell
• 5. Immunity decreases with age, virus persist in nerve ganglia & can infect skin, causing shingles
• 6. Transmission to others occurs from respiratory secretions and skin

• S/S: Itchy bumps & blisters in various stages, fever
• Latent infections can reactivate, resulting in shingles years later
• Incub: 10-21 days
• Cause: Varicella-zoster virus; enveloped double-stranded DNA virus

• Multiplication in upper respiratory tract followed by dissemination via bloodstream to the skin
• Cytopathic effect of virus includes giant cell formation

• highly infectious
• Acquired by respiratory route
• People infected with either chickenpox or shingles the only source
• Spread via skin lesions and respiratory secretions

• Acyclovir or similar antiviral med for prevention and tx
• Attenuated vaccine
• Passive immunization with zoster immune globulin (VZIG) for immunocompromised individuals

• Measles
• 1. Airborne infects eyes and upper respiratory tract, then lymph nodes in region
• 2. Virus enters bloodstream and is carried to all parts of body, including brain, lungs and skin
• 3. Skin cells infected are attacked by cytotoxic T cells, causing generalized rash
• 4. Virus replicating in lungs can cause pneumonia, brain can also be infected
• 5. Rare cases, virus persisting in brain causes sclerosing panencephalitis, months or years after acute infection
• 6. Secondary infection of ears and lungs common
• 7. Transmission is by respiratory secretions

• Will start from head and go down
• Have Koplik Spots, which look like grains of salt lying on red and rough oral mucosa, seen inside checks
• Rash, fever, weepy eyes, cough, nasal discharge

• Measles
• Rubeola virus, a single-stranded RNA virus of paramyxovirus family

• Virus multiplies in respiratory tract
• Spreads to lymphatic tissues, then to all parts of body, notably skin, lungs and brain
• Damage to respiratory tract epithelium leads to secondary infection of ears and lungs

• Acquired by respiratory route; highly contagious
• humans only source

• No antiviral tx currently available
• Attenuated vaccine after age 12 mon
• second dose on entering elementary school or at adolescence

• German measles
• 1. Airborne infects nose and throat
• 2. Virus taken up by lymph nodes in region
• 3. Rubella multiples and enters bloodstream
• 4. Circulating virus reacts with antibodies, resulting in immune complexes
• 5. Immune complexes lodge in skin, causing rash, and in joints causing pain
• 6. In prego women, rubella crosses placenta, infecting fetus, resulting in congenital rubella syndrome
• 7. Transmission to others is by respiratory secretions

• Abnormalities include cataracts and other eye defects, brain damage, heart defects, and low birth weight despite normal gestation
• Babies may be stillborn
• Those that live continue to excrete rubella in throat secretions and urine from many months

Most are asymptomatic: mild fever and cold sx, rash beginning on forehead and face, enlarged lymph nodes behind ear

Cause: Rubella virus, an RNA virus of togavirus family

• Following replication in upper respiratory tract, virus spreads to all parts of body and crosses placenta
• Surviving fetuses often develop abnormally, they excrete virus for months after birth

• German measles
• Virus possibly present in nose and throat from 1 week before rash to 1 week after
• Infection occurs via respiratory route
• Humans are only source

• No specific antiviral tx
• Attenuated vaccine administered to children at 12 to 16 months, repeated at 4-6 yrs of age

group of molds that invade hair, nails and the keratinized portion of skin

• caused by papillomaviruses
• Can survive on inanimate objects
• Can be treated effectively by removing all abnormal cells
• Done by freezing, cauterizing, or surgically removing

• Involves Epidermophyton, Microsporum, or Trichophyton species
• Fungi invade keratinized skin, causing commonly known athlete's foot, jock itch, and ringworm

• Yeasts
• Both are usually harmless on skin, but M. furfur sometimes causes skin conditions such as scaly face rash, dandruff, or tinea versicolor

C. albicans sometimes invades deeper layers and subcutaneous tissues